Method for pattern reproduction



METHOD FOR PATTERN REPRODUCTION Filed Jan. 5, 1.955 2 Sheets-Sheet 1FORM ELECTROSTATIC IMAGE OF PATTERN ON XEROGRAPHIC PLATE DEVELOPELECTROSTATIC PATTERN WITH TACKIFIABLE DEVELOPING POWDER TRANSFERDEVELOPED POWDER PATTERN TO CARBON SHEET OF DUPLICATING CARBON SETSUPERPOSE MASTER SHEET OF DUPLICATING CARBON SET ON CARBON SHEETTACKIF'Y POWDER PATTERN IN CONTACT WITH CARBON B MASTER SHEETS FIG. 9

SEPARATE MASTER SHEET FROM CARBON SHEET INVENTOR. LEWIS E. WALKUP HOWARDALBRECHT BY 5A A WW ATTORNEY FIG. I

Nov. 5, 1963 L. E. WALKUP ETAL 3,109,367

METHOD FOR PATTERN REPRODUCTION 2 Sheets-Sheet 2 Filed Jan- 3, 1955 FIG.6

FIG. 2

FIG?

FIG. 3

FIG. 8

INVENTOR LEWIS E. WALKUP BY HOWARD ALBRECHT MA A 5% TORNEY FIG. 5

United States Patent 3,109,367 METHOD FOR PATTERN REPRODUCTION Lewis E.Walkup and Howard W. Albrecht, Columbus,

Ohio, assignors, by mesne assignments, to Xerox Corporation, acorporation of New York Filed Jan. 3, 1955, Ser. No. 479,453 1 Claim.(Cl. 101149.4)

This invention relates to the field of pattern reproduction andparticularly to a method of and apparatus for aflixing a predeterminedpattern of loosely cohesive pattern material to a firmly cohesivesupporting material.

In many commercial and industrial fields, it is frequently necessary ordesirable to form and/ or reproduce a given pattern or outline in aspecific material that does not readily lend itself to convenient orrapid methods of application. A typical example of this situation is ofcomon occurrence in the field of liquid or spirit duplication for theproduction of copies of printed material. In this process, the copy tobe reproduced is typed or written on the master sheet of a spiritduplicating set which includes a carbon sheet comprising a looselycoherent layer of dye containing material mounted on a relatively smoothbacking sheet so that the dye containing material may readily bestripped therefrom. The dye containing layer of the carbon sheet isarranged in juxtaposition to the master sheet, and the pressure of thetype or writing instrument causes a quantity of dye from the carbonsheet to be deposited on the back of the master sheet in a patterncorresponding to that appearing on the front of the master sheet. Whenthe master is completed, it is placed on the rotating drum of aduplicating machine. As copy paper is fed into the machine, it ismoistened slightly, usually with an alcohol base dye solvent, as itcomes in contact with either a roller or wick. Relatively little of thesolvent is applied so that it evaporates quickly, but it is sufiicientto pick up a thin layer of dye from the master and this dye remains onthe copy paper in the form of the pattern deposited on the master sheet.

For the reproduction of typewritten copy, this process is quite adequateand is widely used, although the typist must exercise somewhat more thanusual care in centering and laying out the work. A limitation of theprocess is that a constant typing pressure must be maintained in orderto deposit a dye pattern of uniform thickness on the back of the mastersheet. In the event the dye pattern is not of uniform thicknessthroughout, the thinner portions of dye are expended more quickly thanthe remainder of the dye pattern, with the result that the num ber ofcomplete copies that can be made is limited by the thickness of the dyepattern in its thinnest portion. A further limitation is that thecorrection of typographical errors must be efieoted directly on themaster sheet and requires substantially more time and effort than inconventional typing practice, and usually results in noticeable defectsin the finished copy.

When the process is applied to the reproduction of written copy, linework, or art work, it becomes particularly cumbersome and unwieldly. Inthese cases, it is currently required that the desired copy be formeddirectly on the face of the master sheet in the exact form in which itis to be reproduced and that the writing or drawing pressure bemaintained constant throughout in order to deposit a dye pattern ofuniform thickness on the reverse side of the master sheet in exactcorrespondence with the line copy pattern formed on the front. Suchpractice obviously requires the services of a skilled artist ordraftsman and, at best, is extremely expensive and time consuming.Furthermore, in its present form, the spirit duplicating processprovides no method to make reproductions of existing copy such asprints, drawings, letter- 3 199,367 Patented Nov. 5, 1963 heads, orother forms of line copy, because there is no convenient method forforming a dye pattern on the master sheet that corresponds to the linecopy pattern that should be reproduced.

In order to overcome the above described limitations in the spiritduplicating field and to provide a convenient process for use in otherfields in which comparable problems exist, the present invention affordsas its principal object a method of and apparatus for aflixing apredetermined pattern of loosely cohesive pattern material to a firmlycohesive supporting material. A. further object of the invention is toafford a method of and means for forming such a pattern that is ofuniform thickness throughout its entire area. A further object is toimprove the technique of pattern transfer wherein all pattern errors mayconveniently be corrected before transfer is effected. A further objectis to afford an improved method and apparatus for preparing duplicatingmasters for use in spirit or liquid duplicating processes.

Briefly, these and other objects of the invention are attained by anapplication of the art of xerography wherein a latent electrostaticimage of the predetermined pattern is formed and is coated with aneleotroscopic powder of a type that can be caused to adhere to thesupporting material on which the ultimate pattern is to be formed aswell as to the material of which it is desired that such pattern becomposed. Preferably, the powder image corresponding to the desiredpredetermined pattern is formed or or transferred to one of a pair ofsuperposable sheets, one of which includes a firmly coherent layer ofsupporting material and the other of which includes a loosely coherentlayer of pattern material. The sheets are then superposed with thepowder image positioned therebetween and the powder image is caused toadhere to the surfaces of both sheets and bond them firmly together.When the bonding of the several materials is completed, the superposedsheets are forcibly separated whereby an area of the pattern. materialcorresponding to the predetermined pattern is literally pulled from thelayer of pattern material and is firmly affixed to the layer ofsupporting material.

Specifically, as the process is applied in the field of spiritduplicating, the electrostatic image of the predetermined pattern isdevelopedwith a xerographic developer including an electroscopicpowdered resin which, when tackified under suitable conditions of heatand pressure, is capable of adhering firmly to the dye layer of thecarbon sheet of a spirit duplicating set as well as to the surface ofthe master sheet thereof. After the pattern is formed and developed itis transferred electrostatically to the dye coated surface of the carbonsheet of a spirit duplicating set and the master sheet of the set issuperposed thereon. The assembled set is then placed betweenthermostatically controlled platens of a hydraulic press wherein apredetermined pressure and temperature are applied for a sufiicientperiod of time to tackify the powdered resin and cause it to adhere tothe dye coated surface of the carbon sheet as well as to the surface ofthe master sheet. The sheets of the duplicating set are then forciblyseparated so that a dye pattern of uniform thickness and conformingexactly to the predetermined pattern is pulled from the loosely cohesivedye layer of the carbon sheet and is firmly afiixed to the master sheet,thereby forming a dye coated master sheet that may be used directly inthe usual manner in a spirit duplicating machine.

The term tackified and the several variant forms thereof used throughoutthe specifications are employed to define the condition of the powderparticles when treated in a manner such that the individual particlessoften and coalesce and in which state they become sticky and readilyadhere to other surfaces. Although this conamass? dition necessarilyrequires a flowing together of the particles to effect a thorough fusionthereof, it is to be understood that the extent of such flowing is notsuflicient to extend beyond the boundary of the pattern in which theparticles are formed.

The method of the invention and a suitable device for effecting aspecific application thereof are shown in the appended drawings, inwhich:

FIG. 1 is a flow diagram illustrating the several steps of the method.of the invention, as applied in forming a predetermined pattern of dyematerial on a master sheet for use in a spirit duplicating process;

FIGS. 2 through 8, inclusive, are schematic illustrations of the severalsteps of the method of FIG. 1, wherein FIG. 2 is a plan view of axerographic plate bearing an electrostatic image of a predeterminedpattern :fiormed thereon;

FIG. 3 is a plan view of the xerographic plate of FIG. 2 wherein thelatent image of the predetermined pattern is developed with atackifiable developing powder;

FIG. 4 is a plan view of a portion of a carbon sheet of a carbonduplicating set to which the powder pattern of FIG. 3 has beentransferred;

FIG. 5 is a sectional view of the carbon sheet and powder pattern takenon the line 5-5 of FIG. 4;

FIG. 6 is a sectional View of the elements of FIG. 4 after the mastersheet is superposed thereon;

FIG. 7 is a sectional view of the elements of FIG. 6 after the powderpattern is tackified;

FIG. 8 is a sectional View illustrating the relationship of the severalelements of FIG. 7 while the master and carbon sheets of the duplicatingcarbon set are being separated;

FIG. 9 is a schematic front elevation of a thermo statically controlledhydraulic press suitable for use in the practice of the invention.

In the practice of the method of invention, as applied in the field ofspirit duplicating, the pattern to be reproduced is conveniently formedon one of the sheets of a spirit duplicating set. Such sets are ingeneral commercial use and many types of these sets are available fromvarious manufacturers. In general, each set comprises .a master sheetand a carbon sheet attached along one edge by a suitable hinge. The setmay also include a separating sheet to prevent smudging of the carbonsheet during handling but which is removed prior to the actual use ofthe set. The master sheet usually comprises a firmly coherent, smoothsurfaced sheet of white paper that is readily receptive of impressionsfrom typewriter type or conventional writing instruments. The carbonsheet comprises a firmly coherent, backing sheet of relatively glossysurfaced paper on which a thin layer of dye material or dye intermediatematerial is uniformly spread. The dye material is usually suspended in awax coating or similar form of binder to make it adhere to the carbonsheet, and the particles of such coating are only loosely coherent witheach other whereby the pressure applied by a writing instrument or typeface readily detaches the impressed portion from the remainder of thedye layer. Also, since the carbon backing sheet has a smoother surfacethan the master sheet, the dye layer in usual practice adheres morereadily method of the invention.

In the process of xerography, as disclosed in Carlson Patent 2,297,691,issued October 6, 1942, a plate comprising a coating of photoconductiveinsulating material on a conductive backing is given a uniform electriccharge over its surface and is then exposed to the subject matter to bereproduced, usually by conventional projection techniques. This exposuredischarges the plate areas in accordance with the light intensity whichreaches them, thereby creating an electrostatic latent image on or inthe plate coating. Development of the image is effected with afinely-divided material such as an electroscopic powder which is broughtinto contact with the coating and is held thereon electrostatically in apattern corresponding to the electrostatic latent image.

The developing agent employed may be of any convenient type suitable tothe requirements of the particular application, the type disclosed inPatent 2,618,551, issued November 18, 1952, being illustrative of a formthat may be used in most instances. As disclosed in this patent, thedeveloper comprises a combination of coated glass bead carriers togetherwith toner powder which comprises particles of fusible resin in which apigment such as carbon is bonded. These components are mixed together toestablish an electrostatic charge on the powder particles that is ofopposite polarity to the charge comprising the latent xerographic imagewhereby, when the developer is cascaded over an exposed xerographicplate, the resin and carbon black particles adhere to the chargedsurfaces of the plate and form a'powder image or pattern of the latentimage previously formed thereon. In the general application ofXerography the resin particles are subsequently bonded to the finishedcopy by the application of heat and serve to secure the carbon blackparticles which provide the coloring matter in the finished copy. In thepresent application the resin particles form the essential element ofthe powder mixture as the bonding agent that unites the ultimate patternmaterial to the supporting material. The carbon black particles servingprimarily to produce a readily visible image on the xerographic platewhereby an operator may check the completeness of the copy that isformed on the plate. 7 7

Referring to the drawings the several steps of the invention outlined inFIG. 1, as applied to the formation of spirit duplicating masters, areillustrated in FIGS. 2 through 8, inclusive, wherein a Xerographic plate1 (see 'FIG. 2), comprising a layer of photoconductive material mountedon a conductive backing, is provided with a reverse readingelectrostatic image 2 of a predetermined pattern that is formed thereonby conventional Xerographic processes. In this figure, plus signs areemployed to indicate the electrostatic charge forming theelectrostatically to the dye layer 4 of the carbon sheet 5 of a spiritduplicating set (see FIGS. 4 and 5) to form a direct reading patternthereon. The master sheet 6 of the duplicating set is then superposedvon the powder pattern on the carbon sheet (see FIG. 6) and the entireassembly is treated under suitable conditions of heat and pressure, asdescribed below, until the powder pattern is tackified and bonded toboth sheets, as in FIG. 7. When tackification and bonding is completeand the master sheet and the dye layer are firmly united by thecoalesced powder particles of the predetermined pattern, the sheets areseparated either by stripping in the usual manner or by sliding thecarbon sheet over a rod 8 or other rounded surface (as in FIG. 8),whereby the bonded dye particles are cleanly broken from the dye layerremaining on sheet 5. Master sheet 6, to which a dye pattern conformingto the predetermined pattern is firmly affixed, may now be used forproducing copies in a duplicating machine in the usual manner.

The tackification of the powder pattern may be accomplished in any of avariety of devices wherein suitable conditions of temperature andpressure can be attained. A typical device for such a purpose isillustrated in FIG. 9 wherein a pair of flat pressure plates 10 and 11are mounted on vertical guide rods 12 which are supported on a suitablebase plate 13. Preferably, upper plate 10 is fixed to the guide rods andlower plate 11 is mounted for slideable movement thereon. Supported onupper plate 10 is a rectangular steel platen 14 which is stressrelievedand surface-ground to provide a smooth flat surface against which theduplicating carbon set may be pressed. Traversing the space betweenplate 10 and platen 14 is a heating coil 15 which is connected to asuitable power source whereby the entire surface of plate 14 may beheated. An insulating sheet of Transite 16, which is a product of hardpressed board of asbestos and Portland cement manufactured by JohnsManville, or other suitable material may be arranged above coil 15 toprevent undue heating of plate 10. A thermostatic control, asschematically illustrated by thermocouple Wire 15A, may be incorporatedin the power supply line to heating coil 15 to maintain the temperatureof the platen within the required range.

Mounted on lower plate 11 is a layer 17 of sponge rubber or otherresilient material which in turn supports a thin flexible metal sheet orplaten 18, which is preferably formed of copper to afford evendistribution of heat. A hydraulic jack 19 actuated by a handle 20 isprovided to elevate plate 11 to raise platen 18 into engagement withplaten 14 and urge it thereagainst with any desired degree of pressure.By this arrangement of the resiliently mounted flexible platen 18, theentire area of a spirit duplicating set placed thereon can be pressedfirmly against platen 14 to establish uniform pressure between allportions of the master and carbon sheets. Although platen 18 ispreferably formed of copper of .015 to .020 thickness, a wide variety ofmaterials and gauges will obviously produce comparable results.

In general, between tackifying operations, the upper and lower platensof the press are maintained in contact so that the lower platen isheated by conduction from the upper platen. By this means the entireassembly is maintained at an even temperature to facilitate thetackification of the powder pattern.

Although various combinations of temperature and pressure may beemployed, best results are obtained when platen 14 is maintained at atemperature of between 140 to 155 F. and the platens are urged togetherat a pressure between 10 to 15 pounds per square inch. Under theseconditions tackification and bonding of the sheets is effected in aperiod between /2 to 5 minutes. Preferred conditions are l50i3 F. at apressure of 10.5 to 1.4 p.s.i., and a time period of 1.5 to 4 minutes.

If desired, lower pressures may be employed for proportionately longerperiods of time to produce comparable results However, in the eventparticles of dust or lint are present on the pattern, the range between10 to 15 pounds per square inch is found most suitable to eliminatedefects in the finished copy.

Temperatures in excess of 160 have a deleterious efiect on some carbonsheet coatings, and are therefore usually avoided with such coatings.Therefore such temperatures are not recommended. At lower temperatures,pressures up to several hundred pounds per square inch may be appliedwith reasonably satisfactory results. However, in such cases it is foundthat particles of the carbon layer other than those encompassed by thepattern area sometimes adhere to the master sheet and produceundesirable background in the final copy.

Although the invnetion is described with specific refererence to itsapplicaion to the field of spirit duplicating, it is apparent that boththe method and the apparatus may readily be applied in other fields forthe purpose of pattern transfer within the scope of the invention. Forexample, should it be desired that a direct-reading pattern be formed onthe master sheet, as for use in an offset printing process, thereverse-reading powder image on the xerographic plate may be transferreddirectly to the master sheet instead of to the carbon sheet, asdescribed above. Thereafter, the process is carried out in the samemanner by superposing the sheets, tackifying the powder pattern, andseparating the sheets to pull a direct-reading image of pattern materialfrom the carbon sheet. Similarly, numerous other applications of theinvention will be apparent to those skilled in similar or related artswhereby a desired pattern forming material that is dlifficult ofconvenient application or handling may be formed in a 'loosely coherentlayer and bonded to a firmly coherent supporting layer by means of acommon bonding agent that can be conveniently formed into the desiredpattern by xerographic processes. Therefore, it is intended that allmatter contained in this specification be interpreted in an illustrativesense and that the invention be limited only as defined in the appendedclaim.

What is claimed is:

The method of forming a predetermined dye pattern on a master sheet of aspirit duplicating set comprising the steps of:

(a) forming a xerographic powder resinous particle image tackifiable byheat at temperatures of degrees F. and above of such predeterminedpattern on the dye layer deleteriously affected at temperatures above160 degrees F. of the carbon sheet of a spirit duplicating set;

(12) superposing the master sheet of said set on the dye layer of saidcarbon sheet supporting said powder image;

(0) placing said sheets in their superposed relation in a heating pressto tackify and bond said powder image between the surfaces of saidsheets, said press including:

(1) a pair of horizontally arranged pressure plates at least one ofwhich is adapted to be moved vertically toward the other,

(2) a flat rigid steel platen mounted on one of said plates,

(3) a flat flexible platen mounted on the other of said plates andarranged in opposing relationship to the other platen and both being ofa size to accommodate said superposed sheets, said flexible platencomprising:

(a) a layer of resilient material mounted on g the other of said plates,

([1) a thin copper heat conductive sheet about .015 to about .020 inchin thickness supported on said resilient material,

(4) an electrical heating coil arranged between the rigid platen and itsassociated plate to heat the platen thereof,

(5) a thermostatic control connected to said coil and adapted toregulate the temperature of said rigid platen, and,

(6) jack means connected to the movable of said plates to causeengagement of the opposing faces of said platens and exert a pressuretherebetween,

(d) operating the jack of said press to exert about 10 to about 15p.s.i.g. on said superposed sheets for about between /2 minute to about5 minutes while said thermostatic control maintains said rigid platen atbetween about 140 F. to F.;

(e) removing the superposed sheets from said press after expiration ofsaid time period; and,

(f) separating said sheets by sliding the carbon of said set over arounded surface, whereby an area of dye layer corresponding to the areaof the predeter- References Cited in the file of this patent UNITEDSTATES PATENTS Richardson Feb. 10, 1914 Szasz Mar. 9, 1937 8 NeidichOct. 5, 1937 Hess et a1. Sept. 2, 1941 Carlson Oct. 6, 1942 CarlsonSept. 12, 1944 Bungay Jan. 6, 1953 Dorman et a1 Mar. 20, 1956

